(1) Field of the Invention
The present invention relates to an image forming apparatus in which a sensitive image forming element is placed in an exposed condition when an open/close member is set at an open position.
(2) Description of the Related Art
There is known an image forming apparatus, such as an electrophotographic copier, a printing press, a printer, a facsimile or a composite system having two or more such image forming capabilities. Such an image forming apparatus is provided with an open/close member which is retractable. During a normal operation of the image forming apparatus, the open/close member is set at a closed position. When any image forming element of the image forming apparatus needs replacement or repair, or when a jam or the like occurs, the open/close member is set at an open position, so that an operator can look into the inside of the image forming apparatus and can perform the replacement or the repair.
Generally, the image forming apparatus includes sensitive image forming elements which are sensitive to dirt and oil and should not be touched. For example, a photoconductive medium and an intermediate transfer medium, which serve as an image support for supporting a toner image thereon, are sensitive to dirt or oil and should not be touched. If the operator touches the photoconductive medium or the intermediate transfer medium, the fingerprint or oil sticks to the surface of such image supports. The quality of an image which is subsequently formed with the affected image forming elements is considerably degraded.
When the image forming apparatus is configured such that the sensitive image forming element is placed in an exposed condition when the open/close member is set at the open position, it is difficult to avoid that the operator erroneously touches the sensitive image forming element which is placed in the exposed condition.
In addition, the image forming apparatus includes sensitive image forming elements which are subject to dirt or oil and affect an operability of replacement or repair of the operator. For example, a toner case is subject to the toner and affects the operability of replacement or repair of the operator. When the image forming apparatus is configured such that the sensitive image forming element is placed in an exposed condition when the open/close member is set at the open position, it is difficult to avoid that the operator erroneously touches the sensitive image forming element which is placed in the exposed condition. Hereinafter, the image forming elements which are sensitive to dirt or oil and the image forming elements which are subject to dirt or oil are collectively called the sensitive image forming elements.
Japanese Laid-Open Patent Application No. 5-72910 discloses an image forming apparatus which utilizes the intermediate transfer medium. When a jam of a recording sheet occurs in the image forming apparatus, a region of a sheet transport path near resist rollers can be placed in an exposed condition so that removal of the recording sheet can be done by the operator. A side surface of the intermediate transfer medium is covered by a cover member so as to prevent the operator from erroneously touching the side surface of the intermediate transfer medium during the removal of the recording sheet. However, in the image forming apparatus of the above publication, it is difficult for the cover member to protect an image transfer area of the intermediate transfer medium in which the recording sheet and the intermediate transfer medium contact each other.
Japanese Laid-Open Patent Application No. 8-272229 discloses an image forming apparatus which utilizes the intermediate transfer medium. In the image forming apparatus, the intermediate transfer medium is placed in an exposed condition when an open/close member is set at an open position. When a jam of a recording sheet occurs, the open/close member is rotated to the open position, so that removal of the recording sheet can be done by the operator. A cover member is provided to cover an image transfer area of the intermediate transfer medium. In accordance with the rotation of the open/close member to the open position, the cover member is moved to cover an image transfer area of the intermediate transfer medium in which the recording sheet and the intermediate transfer medium contact each other. Hence, the cover member protects the intermediate transfer medium so as to prevent the operator from erroneously touching the intermediate transfer medium during the removal of the recording sheet.
In the image forming apparatus of the above publication, an intermediate transfer unit including the intermediate transfer medium and the cover member is provided, and the intermediate transfer unit is removable from a main frame of the apparatus when the intermediate transfer unit needs replacement or repair. When a jam occurs in the image forming apparatus, the entire surface of the intermediate transfer medium, confronting the sheet transport path inclusive of the image transfer area, is covered by the cover member. The operator can safely remove the jamming recording sheet from the image forming apparatus without affecting the toner image on the intermediate transfer medium.
In the image forming apparatus of the above publication, after a toner image is transferred to a recording sheet, the recording sheet with the toner image on the back side of the recording sheet is transported to a fixing unit through a sheet transport path above the intermediate transfer medium. In order to produce a good-quality image on the recording sheet, it is necessary to avoid subjecting the toner image on the back side of the recording sheet to friction or vibration when the recording sheet is passed through the sheet transport path from the image transfer area to the fixing unit.
However, in the image forming apparatus of the above publication, the cover member is located to cover the image transfer area of the intermediate transfer medium which interferes with the sheet transport path. When the recording sheet is passed through the sheet transport path, the toner image on the back side of the recording sheet may be subjected to friction or vibration by the interference with the cover member. Also, the recording sheet when it is being passed through the sheet transport path tends to be lowered by the gravity. However, the image forming apparatus of the above publication is not provided with a holding unit which effectively holds the recording sheet at a lifted position against the gravity when the recording sheet is being passed through the sheet transport path.
In the image forming apparatus of the above publication, if the toner image on the back side of the recording sheet is subjected to friction or vibration when the recording sheet is passed through the sheet transport path from the image transfer area to the fixing unit, the quality of an image which is formed from the affected toner image on the back side of the recording sheet is considerably degraded.